Please read the abstract in the dissertation. Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Chemical Engineering / unrestricted

Temperature and relative humidity of produce throughout the cold chain can greatly affect the quality and safety of the food product. Different packaging systems or containers can provide better cooling environments for food products that could decrease temperature abuse and ultimately safety risks. In this study we compiled temperature and relative humidity profiles of broccoli packed in different shipping containers throughout the produce supply chain. The shipping containers looked at were the wax corrugated box, reusable plastic containers (RPC), and Eco Pack Green Box with and without a lid. Large differences were seen in the temperature profiles of each package during the first 15 hours of the cold chain with the wax-corrugated boxes showing the slowest rate of cooling. Growth rates of Salmonella sp. and Listeria monocytogeneson broccoli at different temperatures were also determined. Salmonella sp.showed a greater ability to grow on inoculated broccoli than Listeria monocytogenesduring higher temperatures such as 20° C and 37° C. Temperature profiles along with microbial counts from produce lots have been previously recorded; this is the first study to record temperature and relative humidity profiles in conjunction with bacterial growth data of lab inoculated produce.

Graphene is a semimetal with zero band gap. Position of Fermi level can be changed by applied gate voltage, which results in a change of free carier concentration. This work focuses on a simultaneous measurement of surface potential by Kelvin probe force microscopy (KPFM) and transport response of graphene Hall bars in different relative humidities and with applying gate voltage. The transport response was also observed in case of graphene Hall bar structure modified by local anodic oxidation (LAO).

The achievement of this thesis is to design functional equipment which is able to measure the basic meteorological variables as air temperature, humidity and barometric pressure. In order to measure relative humidity completed with temperature, an intelligent sensor manufactured by Intersema Inc., MS5534B, was chosen. Relative humidity is measured by a capacitance sensor Humirel HS1101LF. The measured data are stored in anon-volatile memory. Data can be downloaded to a computer file via serial port or they can be online displayed on the computer screen via the wireless Bluetooth connection. Because the equipment is supposed to be used for the external measurement without the connection to electricity, low power consumption was considered as a most important parameter as well as good weather protection.

The main objective of the research was to study the effect of the Stenotaphrum secundatum and Zoysia japonica grasses on the higher and lower environment temperature and lower relative humidity; the secondary objective was to compare whether the Stenotaphrum secundatum grass has a greater impact on the environment parameters of comfort than the Zoysia japonica species. Six materials were used for the extensive green roof, each one forming a layer of the system, which were placed on the concrete slab and in an upward direction, including: PVC geomembrane, Polyester asphalt carpet, Pumice stone, Planar geodren, Prepared soil with guano, compost, muss, and Substrate. In order to make measurements of the higher and lower ambient temperature, a digital thermometer and lower relative humidity meter was used. Stenotaphrum secundatum and Zoysia japonica were used as grass species, as they were the most representative of the grasses used in extensive green roofs. The experimentation was carried out for 2 months from September to October of 2021, having built 3 modules of 1000x600mm roofs, including 1module of the concrete roof with ceramic covering and 2 modules of extensive green roof with two types of grass: Stenotaphrum secundatum and Zoysia japonica. The readings of the environment temperature and relative humidity of the higher and lower part were taken in six points of each module to have a greater number of representative measurements. The watering of the 2 green roof modules with grass was carried out twice a week, applying 5L of water per module. The results indicate that the Zoysia japonica grass is the one that presents a better behavior before the higher ambient temperature and that the Stenotaphrum secundatum grass behaves better before the lower ambient temperature and lower relative humidity. The conclusions indicate that the Stenotaphrum secundatum grass behaves better temperature and relative humidity; the two grass types exhibit different behavior.

Maintaining performance and mitigating heat stress of the modern broiler is a challenging task during hot weather conditions. Increased demand of high quality reasonably priced animal protein and predictions of future limited water availability make sustainability and water conservation a worthwhile goal for the poultry industry. The most used form for cooling broilers after wind speed is evaporative cool cell (CC) systems. Though highly effective at cooling the incoming air, they substantially increase the relative humidity inside the house, which hinders the bird’s ability to cool itself through evaporative respiration. Cool cells also utilize mass amounts of water. The objective of this research was to evaluate the effects of sprinkler technology on broiler performance, cooling water usage, inhouse environments, conservation, and sustainability, while providing information on how to successfully utilize sprinkler cooling in conjunction with an evaporative cool cell system.

Electrostatic charge generation in gas-solid fluidized beds is a significant industrial problem. Associated problems include particle agglomeration and particle wall fouling. In the polymerization industry this may result in "sheets" of fused polymer, due to exothermic reaction causing the melting of the polymer, which can fall off and block the distributor plate disrupting fluidizing gas flow. Additionally, blockage of the catalyst feed or the polymer removal system can take place or the product can become non-uniform. All of these problems require shut-down of the reactor which results in lost production time. While this phenomena has been identified for many years, the mechanisms involved are not well understood, especially wall fouling and the distribution of charge within the bed. Isolation of individual parameters such as hydrodynamics, operating conditions, and material involved is necessary to evaluate how each parameter impacts charge generation during fluidization. In this thesis, the fluidization system consisted of a stainless steel column, two online Faraday cups, and a retractable distributor plate. This system allowed for the simultaneous measurement of charge within different regions of the bed: the entrained fine particles, the particles adhered to the column wall, and the bulk of the bed. Additionally, mass and particle size distributions were measured and images of the layer of particles adhered to the column wall were taken for comparison. This allowed for a charge distribution comparison and evaluation of wall fouling. Three different parameters were investigated: duration of fluidization, column wall material, and relative humidity of fluidizing gas. Fluidization time was studied for 15, 30, 60, 120, 180, and 360 min; relative humidity was investigated for 0%, 20%, 40%, 60%, and 80% relative humidity. Both fluidization time and relative humidity were evaluated at four different fluidization gas velocities, two each in the bubbling and slugging flow regimes. Column wall material was evaluated for a stainless steel and carbon steel column at two gas velocities, one each in the bubbling and slugging flow regimes. Fluidization time was found to influence wall fouling in the bubbling flow regime as the particle layer continued to build as fluidization progressed. In the slugging flow regime, the particle layer developed within 15 minutes of the onset of fluidization. The bubbling flow regime was shown to have a greater capacity for charge generation than the slugging flow regime. This was due to the vigorous mixing in the bubbling flow regime resulting in more particle-particle interactions. Column wall material was shown to influence wall fouling in the slugging flow regime due to the differences in surface roughness of the columns. This was due to the particle-wall contacts resulting in frictional charging which is the predominant charging mechanism in this flow regime. Charge was also impacted in the bubbling flow regime in those particles that were adhered to the column wall. Relative humidity was found to influence wall fouling at the lowest gas velocity tested. However, variations in generation of charge occurred at all fluidization gas velocities tested; the charge-to-mass ratios for the particles adhered to the column wall in the slugging flow regime decreased with high relative humidities. This was due to either the formation of a water film layer on the column wall or instantaneous surface water films on the particles throughout fluidization.

In the Peruvian Andes, inadequate housing represents an important problem for the local rural people. Over 3000 meters above sea level, communities suffer from very low indoor temperatures this becomes an issue which affects the health and indoor thermal comfort of the building. At early winter mornings, outdoor temperatures can occasionally go down to -15°C and indoor temperatures can drop below zero. Previous work in the field has been done by the Pontifical Catholic University of Peru PUCP, to address thermal comfort in Langui, Peru involving participatory design techniques, multidisciplinary approaches and a focus on sustainability. Their most recent design is based on an attached passive solar heating system similar to a Trombe wall. The effect of housing environment on human health has been an acknowledged issue for many years. In the area, the occupants live with high levels of air infiltration, dirt floor (soil), simple windows, metallic or wood doors, roof most commonly made of corrugated metal sheets, adobe walls, no additional insulation attached and no house heating system. This thesis aims to contribute to a current body of research on thermal comfort and provide insights on how the building environment in Langui can be improved. The main objective is to improve thermal comfort in residential buildings in Andean regions of Peru. An improvement was made by installing a Heat Transfer Rocket which increased the temperature while the relative-humidity stayed steady. Overall, the study shows that indoor improvements can increase thermal comfort in Andean regions of Peru.

The majority of therapeutic pharmaceutical formulations are presented in the solid form. Moisture is able to play an important role in the functional performance of pharmaceutical solids. Moisture profiling is able to provide novel information with regards to the behaviour of moisture within materials using equilibrium relative humidity as a measurement. The hypothesis investigated explores the changes in equilibrium relative humidity of pharmaceutical material induced by physical, chemical or storage conditions, these are able to be monitored using the innovative moisture profiler system. The aims within this were to primarily validate the moisture profiler and secondly evaluate the effects of moisture on physical forms and with respect to effects of compaction, finally this was compared to conventional characterisation methods. Preliminary explorations were conducted in order to assess the validity of the moisture profiler, from this lactose was selected as a suitable pharmaceutical material for further work. Processing effects were then examined, firstly storage at elevated relative humidity of different forms of lactose were explored, and this was carried out with supplementary analysis. Secondly the effects of tabletting were explored, different compaction forces were investigated to observe if this had any notable effects on equilibrium relative humidity of the different lactose forms. Finally subsequent storage of the compacts were examined in order to explore if there were any changes in the equilibrium relative humidity. / EPSRC and Reckitt Benckiser

Human performance and health are one of the most relevant topics in modern society. Especially at young ages, when academic performance is indispensable. Thus, as the human being spends most of its lifetime inside a building, thermal comfort has become an essential aspect of a room. The aim of the present research is to measure and evaluate the main thermal comfort parameters such as CO2 levels, relative humidity and indoor temperature so the variation in them can be seen in the study rooms of the library of the University of Gävle as there is student use. For it, Rotroninc Measurement Solutions CL11 sensors and a Testo hot wire probe sensor have been used, as well as IDA ICE software simulations for the result validation. From the research, has been seen that even though the VAV air renewal system works as it should, the CO2 level rises up to 1000 ppm, which is not recommended by different thermal comfort ruling institutions. This way, a modification to the ventilation system control is recommended, changing it from temperature control to CO2 level and temperature control. Moreover, it is seen that during the non-opening hours of the library the ventilation systems are disconnected, generating an important energy-saving without altering the thermal comfort of the rooms at the beginning of the day.